If a cat miaows, it makes that crying sound cats make when they want the door opened, or food, or simply company. Miaow is also the noun for the sound itself: a tiny miaow, a loud miaow. This is the usual British spelling; American books almost always write meow. Both are trying to catch the same cry on the page — they are not two different sounds. It is informal and a little playful, fine in speech and in children’s writing. Grown-up news will more often say the cat cried, or just describe the noise, because miaow looks a bit like a comic-strip word. People also type it as a little joke when someone says something sharp, like a cat putting its claws out — only for informal chat. When you “say” the word, you often just make the cat sound.